A fence, such as enola suggests, would virtually insure a quiet flock. Hens are generally quiet critters except for the exuberance they display around egg laying. There is an occasional individual who gets it in her tiny mind to be vocal and sing for the world, just because she feels entitled.
Then there are the outbreaks of noise that are triggered by strange people going by and strange animals appearing near the run. A nice privacy fence would prevent a lot of this sort of racket.
But overall, hens are a rather silent bunch of beasts.
Lol...I agree....squirrels and blue jays set my girls off! Lol!!